In optical communications networks, optical transceiver and transmitter modules are used to transmit optical signals over optical fibers. The optical transceiver or transmitter module includes a laser that generates amplitude modulated optical signals that represent data, which are then transmitted over an optical fiber coupled to the transceiver or transmitter module. Various types of semiconductor lasers are typically used for this purpose, including, for example, VCSELs and edge emitting lasers, which may be further divided into subtypes that include Fabry Perot (FP) and Distributed Feedback (DFB) lasers.
Some optical transmitter or transceiver modules have only a single transmit channel comprising a single laser, which is sometimes referred to as a singlet. Other optical transmitter or transceiver modules have multiple transmit channels comprising multiple lasers. The multi-channel optical transmitter or transceiver module is commonly referred to as a parallel optical transmitter or transceiver module.
There is an ever-increasing demand for optical transmitter or transceiver modules that have increasingly larger numbers of transmit channels. Of course, increasing the number of transmit channels allows the bandwidth capacity of an optical communications network to be increased. In order to meet this demand, it is known to fabricate an array of lasers on a single semiconductor substrate of the electrical subassembly (ESA) of the module. For example, it is known to fabricate a one-dimensional or two-dimensional array of VCSELs on a single semiconductor substrate. Fabricating the VCSELs on a single semiconductor substrate allows the spacing, or pitch, between adjacent VCSELs to be decreased, which, in turn, allows the number of VCSELs that can be integrated on a single semiconductor substrate to be increased. However, the manufacturing yield for this type of semiconductor device is relatively low due to the fact that the semiconductor device is deemed defective and is discarded if even one of the VCSELs of the array is found to be defective. The relatively low manufacturing yield of this type of semiconductor device increases the overall costs of the semiconductor devices.
Because semiconductor devices that have fewer numbers of VCSELs on them can be manufactured with higher yield, and thus at reduced costs, it is known to construct an array of VCSELs by creating an array of multiple semiconductor devices that have either only a singlet VCSEL or a few VCSELs on them. This approach presents other difficulties, however, one of which is the difficulty associated with precisely aligning the VCSELs with their respective optical coupling elements. Consequently, to date, using multiple semiconductor devices having only either a singlet VCSEL or a very small number of VCSELs on them to create a larger array of VCSELs is not a viable solution.
Accordingly, a need exists for an assembly having multiple semiconductor devices with only either a singlet or a very small number of VCSELs on them that can be combined to create a precisely-aligned larger array of VCSELs.